Field verification of the effect of rail pad stiffness on rail corrugation growth

This study presents a field-based investigation into the influence of rail pad stiffness on the growth of rail corrugation through regular measurements of rail surface roughness on an in-service metro line. Rail corrugation is a critical issue in railway systems due to its contribution to increased vibration, noise, and maintenance costs. Despite extensive research on its underlying mechanisms, quantitative validation of mitigation measures under actual operating conditions remains limited. Frequency-domain analysis of the measured rail surface roughness indicates that the dominant corrugation growth mechanism is governed by anti-resonance phenomena in the coupled vehicle–track system. To evaluate a practical countermeasure, rail pads in a curved track section were replaced with lower-stiffness components, and rail surface roughness was measured for approximately 6 years following rail grinding. The results demonstrate that a reduction in rail pad stiffness effectively suppresses corrugation growth. The observed growth behaviour shows that both the growth rate and the saturation amplitude of corrugation are significantly reduced in sections equipped with softer rail pads. This reduction is attributed to a shift in the natural frequencies of the track system, weakening the anti-resonance condition that amplifies dynamic wheel–rail contact forces. These findings provide both quantitative evidence and mechanistic insight, supporting stiffness modification as a practical mitigation measure and contributing to improved track design and maintenance strategies.